Use of dispersant viscosity index improvers in exhaust gas recirculation engines

Abstract

The use in a cooled exhaust gas recirculation (EGR) engine of an olefin copolymer dispersant viscosity index improver to reduce or eliminate oil thickening and sludge formation is provided. Also provided are lubricated cooled EGR engines with ability to pass rigorous oil viscosity and emission standards.

What is claimed is:  
     
         1 . A lubricated engine comprising an exhaust gas recirculation system, whereby exhaust gases comprising soot generated in the combustion in the engine of fuel contact a lubricating oil used to lubricate said engine, wherein said lubricating oil comprises: a base oil, and at least one dispersant viscosity index improver in an amount sufficient to reduce the amount of oil thickening of the lubricating oil.  
     
     
         2 . The engine of  claim 1 , wherein the lubricating oil further comprises an additive selected from the group consisting of zinc dialkyl dithiophosphates, friction modifiers, corrosion inhibitors, extreme pressure agents, antioxidants, defoamants, surfactants, detergents, and pour point depressants.  
     
     
         3 . The engine of  claim 1 , wherein the base oil of the lubricating oil is selected from the group consisting of natural lubricating oils, synthetic lubricating oils, and mixtures thereof.  
     
     
         4 . The engine of  claim 1 , wherein the base oil of the lubricating oil is selected from the group consisting of animal oils, vegetable oils, castor oil, lard oil, liquid petroleum oils, hydrorefined, solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic and mixed paraffinic-naphthenic types, oils of lubricating viscosity derived from coal or shale, poly-alpha-olefins, alkylated aromatics, alkylene oxide polymers, interpolymers, copolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification or etherification, esters of dicarboxylic acids, and silicon oils.  
     
     
         5 . The engine of  claim 1 , wherein the at least one dispersant viscosity index improver in the lubricating oil comprises an olefin copolymer dispersant viscosity index improver.  
     
     
         6 . The engine of  claim 1 , wherein the at least one dispersant viscosity index improver in the lubricating oil comprises is selected from the group consisting of polymethacrylates, ethylene/propylene copolymers, polyisoprene or saturated polyisoprene, and polyisoprene/saturated polyisoprene copolymers.  
     
     
         7 . The engine of  claim 1 , wherein the engine is selected from the group consisting of automotive engines, heavy and light duty truck engines, gasoline combustion engines, diesel engines, hybrid Internal Combustion/electric engines.  
     
     
         8 . The engine of  claim 1 , wherein the at least one dispersant viscosity index improver in the lubricating oil is a highly grafted, multi-functional olefin copolymer that comprises the reaction product of (1) an acylated olefin copolymer, wherein the acylated copolymer comprises copolymers or terpolymers of ethylene and C 3  to C 23  alpha-olefin and optionally a non-conjugated diene or triene on which has been grafted ethylenically unsaturated carboxylic reactants to a level of 0.3 to 0.75 carboxylic groups per 1000 number average molecular weight units (Mn), and (2) a polyamine compound.  
     
     
         9 . The engine of  claim 8 , wherein the polyamine compound is selected from the group consisting of 
 (a) an N-arylphenylenediamine represented by the formula:                           in which R 1  is hydrogen, —NH-aryl, —NH-arylalkyl, —NH-alkyl, or a branched or straight chain radical having from 4 to 24 carbon atoms that can be alkyl, alkenyl, alkoxyl, aralkyl, alkaryl, hydroxyalkyl or aminoalkyl; R 2  is —NH 2 , CH 2 —(CH 2 ) n —NH 2 , CH 2 -aryl-NH 2 , in which n has a value from 1 to 10; and R 3  is hydrogen, alkyl, alkenyl, alkoxyl, aralkyl, alkaryl having from 4 to 24 carbon atoms;    (b) an aminothiazole from the group consisting of aminothiazole, aminobenzothiazole, aminobenzo-thiadiazole and aminoalkylthiazole;    (c) an aminocarbazole represented by the formula:                           in which R and R 1  represent hydrogen or an alkyl, alkenyl or alkoxyl radical having from 1 to 14 carbon atoms; (d) an aminoindole represented by the formula:                           in which R represents hydrogen or an alkyl radical having from 1 to 14 carbon atoms;    (e) an aminopyrrole represented by the formula:                           in which R is a divalent alkylene radical having 2-6 carbon atoms and R 1  is hydrogen or an alkyl radical having from 1 to 14 carbon atoms;    (f) an amino-indazolinone represented by the formula:                           in which R is hydrogen or an alkyl radical having from 1 to 14 carbon atoms;    (g) an aminomercaptotriazole represented by the formula:                           in which R can be absent or is a C 1 -C 10  linear or branched hydrocarbon selected from the group consisting of alkyl, alkenyl, arylalkyl, or aryl;    (h) and an aminoperimidine represented by the formula,                           in which R represents hydrogen or an alkyl or alkoxy radical having from 1 to 14 carbon atoms;    (i) aminoalkyl imidazoles, such as 1-(2-aminoethyl) imidazole, 1-(3-aminopropyl) imidazole; and    (j) aminoalkyl morpholines, such as 4-(3-aminopropyl) morpholine.    
     
     
         10 . The lubricated engine of  claim 1 , wherein the amount of the dispersant viscosity improver in the lubricating oil is from 2 weight percent to about 18 weight percent.  
     
     
         11 . The engine of  claim 1 , wherein the engine is cooled by the circulation of a material selected from the group consisting of water, a water/hydrocarbon mix, water/glycol mix, air, and gas.  
     
     
         12 . The engine of  claim 1 , wherein said lubricated engine achieves a viscosity increase of less than 10 cSt at 100° C. at a soot level of up to 6.0% m in the Mack T-11 test.  
     
     
         13 . The lubricated engine of  claim 1 , wherein the lubricating oil passes the Mack T-11 test at a viscosity increase of less than 8 cSt at 100° C. at a soot level of up to 6.09% m in the Mack T-11 test.  
     
     
         14 . The lubricated engine of  claim 1 , wherein the lubricating oil has a viscosity increase of less than 10 cSt at 100° C. and up to 6.0% m soot in the Mack T-11 test.  
     
     
         15 . The use in an Internal Combustion engine comprising a cooled exhaust gas recirculation system of a lubricating oil comprising a base oil, and at least one olefin copolymer dispersant viscosity index improver in an amount sufficient to reduce the amount of soot-induced oil thickening of the lubricating oil.  
     
     
         16 . A method of reducing the soot-induced thickening of a lubricating oil used to lubricate a cooled exhaust gas recirculating engine in which soot accumulates in the oil, said method comprising lubricating the engine with a lubricating oil comprising a base oil and a sufficient amount of an olefin copolymer dispersant viscosity index improver.  
     
     
         17 . A method of improving fuel economy of a vehicle having a cooled exhaust gas recirculation engine, wherein said method comprises adding to and operating in the crankcase of said vehicle a lubricating oil composition containing a sufficient amount of the olefin copolymer dispersant viscosity index improver described herein.  
     
     
         18 . A method of improving fuel economy durability of a vehicle having a cooled exhaust gas recirculation engine, wherein said method comprises adding to and operating in the crankcase of said vehicle a lubricating oil composition containing a sufficient amount of the olefin copolymer dispersant viscosity index improver described herein.  
     
     
         19 . A method of simultaneously passing the M-11 EGR test, T-10 test (ASTM D4485 classification for API C 1-4  oils), and the Mack T-11 in cooled EGR engine, said method comprising adding to and operating in the crankcase of the engine a lubricating oil composition containing a sufficient amount of the olefin copolymer dispersant viscosity index improver described herein.  
     
     
         20 . A method to give superior oil sludge performance in a vehicle with a cooled EGR engine, said method comprising adding to and operating in the crankcase of the vehicle a lubricating oil composition containing a sufficient amount of the olefin copolymer dispersant viscosity index improver described herein, whereby the oil sludge performance is superior to the oil sludge performance in a cooled EGR engine of an oil without the olefin copolymer dispersant viscosity index improver described herein.  
     
     
         21 . A method to give superior wear protection from soot in a vehicle equipped with a cooled EGR engine, said method comprising adding to and operating in the crankcase of the engine a lubricating oil composition containing a sufficient amount of the olefin copolymer dispersant viscosity index improver described herein, whereby the wear protection from soot is superior to the wear protection from soot in a cooled EGR engine lubricated with an oil without the olefin copolymer dispersant viscosity index improver described herein.  
     
     
         22 . A method to extend the service time between oil drains in a vehicle equipped with an exhaust gas recirculation engine up to about 60,000 miles by the addition to a lubricating oil in the engine of a sufficient amount of an olefin copolymer dispersant viscosity index improver as described herein.